The present invention relates to a magnetic disk drive such as a hard disk drive, and to an information recording system such as a hard disk recorder that uses the magnetic disk drive.
In recent years, various kinds of data including television programs are in general written to hard disks. On the other hand, recording of copyrighted data has required a function of preventing the written data from illegally flowing out or other similar functions. For example, at the time of recording a digital television broadcast, it is not permitted to record a plurality of contents each of which continues one minute or more. For this reason, if data whose length is one minute or more is recorded, an encryption key (issued as license information) is changed at intervals of one minute so that a plurality of keys are not allowed to be used all at once. This is one technique to observe this constraint.
Heretofore, when such a key is changed, the PKI (public key encryption infrastructure) technology which has been developed in parallel with the network technologies is in general used.
To be more specific, as shown in FIG. 6, in the conventional equipment, a host as a hard disk recorder main body authenticates a hard disk as a recording medium, and then transmits an encryption key to the hard disk (S1). Next, the host transmits encrypted license information L (information used to decrypt content data, and the like) to the hard disk (S2) and then transmits data (S3). The hard disk checks this license information L, and writes the data. In addition, there is a request for reproduction concurrent with recording. In this case, subsequent to the writing of the data, the hard disk authenticates the host and then transmits an encryption key (S4). Next, the hard disk transmits encrypted license information L (S5), and then transmits data that has been read out (S6). The host decrypts the read data by use of the license information L to perform reproduction processing. In this conventional example, it is necessary to repeat the above processing from the step S1 before the next data is written. These steps are similar to implementation of the PKI technology in the network.
However, if the conventional steps are used, when reproduction is made concurrently with recording, data with a relatively large amount of information, including information used for authentication and encryption key information, is continuously transmitted and received between the host and the hard disk, in addition to data to be recorded and data to be reproduced. In addition, the length of time required for the authentication processing of the authentication information and the length of time required for encryption and decryption processing of the encryption key are relatively long. Therefore, it is not possible to improve the performance of recording and reproduction.